The trick is not picking arcs just because you like them or because they’re good (then you’ll end up with 9 films like smudger9), but picking arcs that develop Anakin and Obi-Wan as characters and enhance or add to things already present in AOTC and ROTS.
Umbara arc,final ashoka arc, and second battle of Geonosis all develop Anakin as a character.
But the Zygerian slaver arc develops him far more effectively and ties directly into the films with the discussion of Anakin’s past which is why I chose that.